A door trim, a type of interior material, is attached onto a vehicle door inside the vehicle compartment. The door trim is usually formed with synthetic resin material, and an armrest is integrally formed on the surface of the door trim inside the vehicle compartment. The armrest is a shelf that supports the forearm of a vehicle occupant comfortably and protrudes into the vehicle compartment by a predetermined amount. The armrest, during a vehicle collision, may hit an object in the vehicle compartment, thus causing some damage to the object.
To reduce the damage to the object during a vehicle collision, a conventional technique exists in which a notched groove of a substantially triangular shape in cross section is formed at a base portion of an armrest formed on a door trim, for example, as disclosed in Japanese Utility Model Laid-Open No. 6-6123 (FIG. 1 at page 5). The notched groove is formed on the surface of the door trim facing outward from the vehicle compartment, extending in the vehicle longitudinal direction. If the armrest is pressed by the object in the vehicle compartment during a vehicle collision, the notched groove is broken and the armrest is crushed while absorbing the collision energy. This enables a reduction in damage to the object during the vehicle collision.
Recently, the need in the market to reduce vehicle weight has intensified and door trims are no exception. To reduce the vehicle weight, resin foam material has been used as a material for automotive interior materials, such as door trim and the like.
Inventors of the present invention, as described below, have attempted to use resin foam material to form a door trim capable of reducing damage to an object during a vehicle collision.
As shown in FIG. 6, a cavity CV is formed between an opposing movable mold 7 and stationary mold 8 which are disposed vertically. On the surface of the stationary mold 8 that forms the cavity CV, there is formed a protrusion portion 81 of a substantially triangular shape in cross section. The protrusion portion 81 is formed extending in a vertical direction relative to the plane of the paper in FIG. 6.
As shown in FIG. 7, after the molten resin material SR added with a foaming agent is supplied into the cavity CV, the movable mold 7 is moved away from the stationary mold 8 to open the movable mold 7 by a predetermined amount. This causes the molten resin material SR to foam and a door trim 9 is formed. The operation of opening the movable mold 7 by the predetermined amount to foam the molten resin material SR may be called core-back. At core-back, a notched groove 91 is formed by the protrusion portion 81 on the surface of the door trim 9 in contact with the stationary mold 8.
As shown in FIG. 7, a portion forming the notched groove 91 of the door trim 9 is smaller than any other portion in thickness. Accordingly, the portion forming the notched groove 91 has a reduced volume of resin material due to the reduced thickness and does not have sufficient thickness even after the resin material is foamed. In this case, on the surface of the door trim 9 in contact with the movable mold 7, a depression 92 is unavoidably formed at a location opposite to the notched groove 91. Formation of the depression 92 on a decorative surface of the door trim 9 (the surface in contact with the movable mold 7) will impair the appearance of the door trim 9.